Method and apparatus for shifting a typing element

ABSTRACT

A multicharacter-type element is shifted a relatively long distance between alternate case positions by motion normally employed for selecting individual characters for printing. Case shift movement of the type element is divided into sequential portions that extend in combination through a large amount of the time available in an ordinary character printing operation whereby the dynamics of the system are maintained compatible with the character printing function. Control of the shift operation is obtained from a novel shift key mechanism that operates like a character key when either depressed or released.

United States Patent Inventor John O'Neill Schaeler Lexington, Ky.

Appl No. 837,849

Filed June 30, 1969 Patented June 1, 1971 Assignee International Business Machines Corporation Armonk, N.Y.

METHOD AND APPARATUS FOR SHIFTING A TYPING ELEMENT 16 (Claims, 3 Drawing Figs.

U.S. CI 197/71, 197/16 int. Cl B4lj 25/24 Field of Search 197/71, 16

References Cited UNITED STATES PATENTS 3,157,265 11/1964 Palmer 197/16 3,386,554 6/1968 Everhard 197/16X 3,453,379 7/1969 Holmes 197/16X 3,516,528 6/1970 Davidge et a1, 197/71X Primary ExaminerRobert E. Pulfrey Assistant Examiner-C. Cougheivour Attorneys Hanifin and .lancin and E. Ronald C offma ABSTRACT: A multicharacter-type element is shifted a relatively long distance between alternate case positions by morion normally employed for selecting individual characters for printing. Case shift movement of the type element is divided into sequential portions that extend in combination through a large amount of the time available in an ordinary character printing operation whereby the dynamics of the system are maintained compatible with the character printing function.

Control of the shift operation is obtained from a novel shift key mechanism that operates like a character key when either depressed or released.

mimium new 3581; 860

SHEET 1 OF 2 FIG. 2

INVENTOR.

JOHN 0. SCHAEFER ama ATTORNEY.

PATENTEU JUN 1|97| 3581 860 sum 2 or 2 METHOD AND APPARATUS FOR SHIFTING A TYPING ELEMENT BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to serial printers of the type having a type element that is divided into alternate groups or cases of individual types. Positioning of the type element is limited to characters within a single operatively positioned one of such groups. To select a character from a group not in operative position, a so-called shift function must be performed. This function displaces the type element a relatively large amount compared to motion available for character selection and operates in sequence with other typing functions such as printing and spacing.

2. Description of the Prior Art Traditionally, the case shift function has been performed by mechanism independent of ordinary character selection mechanism. This traditional approach allows for independent design of the shift mechanism to accommodate the dynamics inherent in the relatively large displacement of the type element in a manner suitable to the needs of the shift function alone. An example of this approach to the shift function is provided by U.S. Pat. No. 2,9l9,002.

SUMMARY OF THE INVENTION This invention eliminates the need for an independent mechanism for performing the shift function by employing powered motion normally available for selecting individual characters. A problem is raised due to the dynamics that accompany moving the type element through a relatively large increment by employing timed motion normally designed to operate through small increments to move the type element from a home position to a selected character position and then to restore the type element from the selected character position to its home position. My invention manages this dynamic problem by dividing the total available cyclic motion into a pair of serial part cycle increments. During one portion of cyclic motion the type element is moved partway through its travel between cases. Then the type element is moved the remainder of its travel during the other portion of the total available motion.v

More specifically, performance of a shift operation is accomplished by moving a case shift member through its entire stroke from one case to the other during one portion of available character selection motion. This full stroke motion is coupled with simultaneous motion of an interconnected character selecting member in a direction subtractive of the motion of the case shift member such that only a part of the total motion of the case shift member is delivered to the type element. The subtracted case shift motion is delivered to the type element by the character selecting member as it is moved during the other portion of its cyclic operation.

Control of theshift operation is accomplished from a shift key control mechanism that is similar to character selection key mechanisms described in U.S. Pat. No. 3,086,635, but is operated both upon depression and release of the shift key. A bellcrank mounted on the keylever moves bodily downwardly upon depression of the shift key and also pivots to move downwardly upon release of the shift key. Either type of bellcrank downward movement operates the shift control mechanism.

These and other objects, features and advantages of my invention will be apparent to those skilled in the art from the following detailed description of my shift method and an illustrative preferred implementation thereof, wherein reference is made to the accompanying drawings, of which:

FIG. 1 is an abstract operational view of selected machine components illustrating the steps of my method and the principals of operation of my device;

FIG. 2 is a perspective view of a typewriter mechanism capable of performing my method and including shift function apparatus that is unique in and of itself, together with a shift key mechanism for controlling the shift function apparatus; and

FIG. 3 is an enlarged fragmentary view of a portion of the mechanism shown in FIG. 2.

The basic steps of my method are illustrated in FIG. 1 which shows a typewriter-type element 10 carrying a plurality of characters 11 that are divided into two alternately active subpluralities or cases 12 and 13. The type element 10 opposes a paper holding platen 14 to define a printing position 15. Any one of the characters 11 from the active case 12 or 13 may be aligned with printing position 15 by displacement of a, character selection arm or member 20 from its normal full line I or home position 2] shown, to any of a plurality of displaced positions indicated by increment lines 22. The displacement of type element 10 to selectively activate either case 12 or 13 is accomplished by positioning of case shift arm or member 23 in either its full or broken line position respectively. The motions of character selection member 20 and case shift member 23 are interconnected by a differential transmission mechanism comprising tape, strand or cord 24 that spans pulleys 25 and 26, is grounded relative to the rotational shaft 27 of the type element 10 at post 28, and is connected to type element pulley 29 in opposition to a restore rotate spring, not shown. The mechanism thus far described is essentially identical to that disclosed in aforesaid U.S. Pat. No. 2,919,002.

The cyclic operation for shifting the type element 10 to case 13 from case 12 as shown in full lines in FIG. 1, involves displacement of case shift member 23 to its broken line position while simultaneously displacing the character selection member 20 to its broken line position. Case shift member 23 is then retained in its broken line position while character selection member 20 is returned to its full line position.

Displacement of case shift member 23 from its full line to its broken line position tends to rotate the type element 10 counterclockwise a distance of l 1 units or character location incre ments. The displacement of character selection member 20 tends to rotate the type element 10 five units clockwise which is subtractive of the counterclockwise movement caused by case shift member 23. Simultaneous movement of both members 23 and 20 thus results in actual rotation of the type element l0 counterclockwise by six units. This operating parts of the system thus are subjected, during this portion of the cycle, to dynamics associated with type element displacement of six clockwise units.

During the motion of character selection member 20 as it returns to its full line position, the type element 10 is rotated counterclockwise by five units to complete the total shift motion of 11 units. During this portion of the shift motion, operating parts of the system are subjected to dynamics associated with five units of motion of the type element 10. The dynamics of this shift operation principally involve considerations of acceleration and the resultant loading on the differential transmission tape 24 and the type element 10 reacting against the rotate spring that is not shown.

Cyclic operation for returning the type element 10 to case 12 involves a mirror image of the previously described shift operation. The first action to occur is displacement of the character selection member 20 to its broken line position to move the type element 10 five units clockwise. Next, case shift member 23 is moved to its full line position while character selection member 20 is simultaneously restored to its full line position to produce a resultant clockwise motion of six units of the type element 10. This six units is the algebraic result of ll clockwise units of motion provided by case shift member 23, and five counterclockwise units of motion of character selection member 20. The dynamics of this shift operation 1 l considerations of acceleration and cycle overrun as the machine components are driven by the type element restore spring (not shown).

It will be recognized that the method thus described can be performed by various substantially different and nonequivalent selection apparatus of the restore-to-home configuration. An example of appropriate selection apparatus different from that disclosed in aforesaid U.S. Pat. No. 2,919,002 may be found in U.S. Pat. No. 2,847,105.

FIGS. 2 and 3 show a preferred specific embodiment of mechanism for performing the method described above in a typewriter or printer T generally constructed like that disclosed in U.S. Pat. No. 2,919,002. This typewriter T includes a keyboard 30 of the type generally described in the aforesaid U.S. Pat. No. 3,086,635 having a plurality of character keylevers 31 operable by keybuttons 32 to activate associated encoding interposers 33. An activated interposer 33 initiates a cycle by depression of cycle bail 34 to operate a selectively activatable source of cyclic motion such as a clutch 35. The interposer 33 also selectively moves one or more encoding bails 36 thereby setting the printer T into operation for printing an individual character. Typewriter T includes a multidisplacement character selection motion converter or so-called wiffel tree latch selector 40 like that of aforesaid U.S. Pat. No. 2,919,002 for generating varied incremental amounts of motion on output rod 41 that is connected to character selection member 50 to position it in any of l 1 unique positions including a home position-as shown. Operation of the output rod 41 is timed with respect to the operation of other printing structure within the typewriter T by the contour on cams 42 mounted on shaft 43 which rotates through 360 during each printing cycle. The motion generated for driving character selection member 50 counterclockwise follows the oscillatory motion of a latch drive bail or chopper bar 44 that moves downwardly and then restores upwardly by the cam 42 and its restore spring 45 respectively. A similar bail 46 driven by a cam 47 also mounted on shaft 43 operates to oscillate the character selection member 50 first clockwise then counterclockwise.

Character selection member 50 is connected by pulley 51 and steel motion transmission tape or strand 52 to pulley 53 connected through shaft 54 to spherical type element 55. counterclockwise motion of selection arm 50 acts against impositive resilient spiral spring 56 connected to the pulley 53. Tape 52 is also connected to case shift mechanism 60 including a case shift arm or member 61 that carries a pulley 62. Tape 52 is grounded with respect to the axis of the type element 55 by a pin 57. As described in U.S. Pat. No. 2,919,002, both the type element 55 and the pin 57 are mounted on a carrier 70 that is displaceable under the control of an escapement mechanism 71 more completely disclosed in U.S. Pat. No. 3,059,751 for letter space movement with respect to a stationary paper holding platen 72. Power and motion are transmitted to the carrier 70 through shaft 73 to cause print impact, ribbon feed and other functions incident to printing. The details of this mechanism are fully described in U.S. Pat. No. 2,879,876.

The mechanism for displacing the shift arm 61 is substantially different from that disclosed in aforesaid U.S. Pat. No. 2,919,002. The shift mechanism 60 of the present invention employs motion taken from the cyclically rotating cam shaft 43 for displacing the arm 61 from its position as shown where it rests against a frame supported stop 63, to a clockwise displaced position where it is retained by a latch 80 acting against a latch reaction surface 64 of the shift arm 61. Motion from shaft 43 is communicated in any convenient manner. For example, my invention delivers oscillatory motion from bail 44 via a selectively activatable motion converter 90 that includes a bellcrank 91 pivoted to the machine frame at 92 and connected to a motion transfer rod or push member 93 to displace it leftwardly upon downward motion of bail 44. Rod 93 is slidably and pivotally mounted on the machine frame by pin and slot connection 94. The right end of rod 93 includes a force transfer surface 95 that can be selectively activated by forward movement to a position of opposition to a tab 65 of the shift arm 61 so as to drive the shift arm 61 clockwise upon leftward movement of the rod 93. The geometry of the bellcrank 91 and shift arm 61 are selected such that the shift arm 61 is displaced 11 units clockwise when rod 93 is connected thereto.

A selectively activatable shift control mechanism 100 activates the motion converter while contemporaneously activating cycle clutch 35, and controlling the character selection motion converter 40 to move arm 50 subtractively with respect to arm 61. In addition, a nonprint" mechanism 74 of the type described in U.S. Pat. No. 3,382,963 and a dead key or nonescape mechanism 75 of the type described in U.S. Pat. No. 3,059,751 are made active through connections to disable the usual functions associated with a print cycle. Shift control mechanism comprises a control link 101 that is pulled leftwardly or to the front of the machine in FIG. 2 by a special keyboard interposer 110 similar in operation to the character interposers 33 of the keyboard 30. Rod 93 is normally urged by spring 96 to the rear of the machine against the side of a frame mounted leaf spring stop 97 where left and right oscillatory motion of the rod 93 has no effect on the shift arm 61. The leaf spring 97 also operates as a storage member for retaining the rod 93 in its forward position once displaced thereto until the oscillatory stroke thereof has been completed.

interposer 110 operates somewhat differently than character interposers 33 in that the interposer 110 is displaced downwardly by either depression or release of its associated two position shift key 111 mounted on keylever 112. Depression of shift key moves a pivoted bellcrank 102 downwardly. A generally vertical arm 103 of the bellcrank 102 flexes a frame mounted leaf spring latch 104. A generally horizontal arm 105 drives a pawl or projection 113 against upstanding arm 114 of the interposer to displace the interposer below its leaf spring latch 110a and trip cycle bail 34 to generate a keyboard cycle in the same manner as interposers 33. In the course of the keyboard cycle, a filter shaft or power means 37 drives interposer 110 leftwardly in FIG. 2 to displace one bail 36 that is associated with the selection member 46 for a purpose more completely described hereinafter. Leftward movement ofinterposer 110 also pulls control link 101 leftwardly to set force transfer surface 95 into alignment with tab 65 of the shift arm 61. From these two actions it can be seen that rotation of cam shaft 43 will operate through rod 93 to drive shift arm 61 eleven units clockwise, and will also act through bail 46 as selected by interposer 110 to drive character selection arm 50 five units clockwise. These simultaneous motions will be recognized as one step of the method disclosed in connection with FIG. 1.

Leftward movement of interposer 110 acts through projection or drive abutment 115 and bellcrank drive surface 106 to drive bellcrank 102 clockwise about its axis 112a to a point where its lower end 107 moves leftwardly of and become trapped by leaf spring latch 104. This clockwise motion of bellcrank 102 causes a leftward displacement of bellcrank end 107 to tension a latch activating bias spring 81 that acts on the latch 107 through rod 82 to overpower latch disabling spring 83. Latch 80 is thus resiliently urged forwardly against the rearward side edge of a leftwardly extending plate 66 of the shift arm 61. As the shift arm 61 completes and slightly exceeds the 11 unit displacement, latch 80 will be urged forwardly by spring 81 into alignment with the latch surface 64 of the shift arm 61 to retain the shift 61 in its clockwise displaced position. It will be recognized that this retaining function is a step of the method disclosed in connection with FIG. 1.

The interposer 110 will be restored rightwardly and upwardly by its spring 116 flexing pawl spring 117 in the process and displacing pawl 113 counterclockwise from its normal downward projecting condition. Shift keylever 112 will remain depressed by the operator as is usual in the case of typewriter shift mechanisms. It will be recognized that as long as keylever 112 is retained depressed, leaf spring latch 104 retains bellcrank end 107 in its leftward position to retain latch 80 engaged with the latch surface 64 of shift arm 61. Although the shift arm 61 and character selection member 50 moved clockwise substantially simultaneously to the point where shift arm 61 was latched by member 80, character selection member 50 thereafter returns to its home position alone as cam shaft d3 completes its 360 of rotation. The restoring motion of character selection member 50 completes one operation of the method disclosed in connection with FIG. 1.

To obtain a return shift operation, i.e., shift to the position shown in FlG. 2, the operator releases keybutton 111 which rises due to its bias spring 118 to lift pawl 113 to a position free of arm 114 whereby spring 117 pulls pawl 113 into operative alignment with the upper surface of arm 114. Continued upward movement of shift keylever 111 pulls bellcrank end 107 clear of latch-104 allowing spring 108 to rotate the bellcrank 102 counterclockwise thus driving the interposer 110 downwardly for the initiation of another keyboard cycle. Release of bellcrank end 107 from latch 104 does not immediately cause release of latch 80 although latch deactivating spring 83 is conditioned to provide an effective bias on the latch 80. Respective engaging surfaces 84 and 64 frictionally cooperate to resist unlatching movement by spring 83. As with the previously described keyboard cycle, the bail 36 associated with cam follower arm 46 will be activated to cause a clockwise displacement of the character selection arm 50. Also, control member 101 will displace rod 93 toward the front of the machine to align force transfer surface 95 with tab 65 of the shift arm 61. Since the shift arm is already displaced however, there will be no immediate contact between force transfer surface 95 and tab 65. As cycle shaft 43 rotates causing character selection member 50 to move clockwise, rod 93 is driven leftwardly toward the point where ledge 95 will engage tab 65. lt will be recognized that this motion of character selection member 50 without simultaneous motion of shift arm 61, is one step in the method described in connection with FIG. 1.

As ledge 95 engages tab 65, the loading between latch 80 and latch surface 64 of shift arm 61 is reduced thus allowing spring 83 to deactivate latch 80 by moving it clockwise. Note that latch 80 is thus released only at the proper time in the cycle of shaft 43. As rod 93 now begins to return rightwardly during the terminal portion of the cycle of the character selection member 50, shift arm 61 will be moved simultaneously counterclockwise to its home position as shown in full lines in FIG. 2 thus completing the final step of the method of my invention. While the force returning shift arm 61 to its home position comes from spring 56, actual movement of arm 61 is limited and controlled by cam 47 and the rotation of shaft 43.

It is a usual practice to employ a cycle clutch 35 such as a spring clutch that is capable of being overrun, i.e., its output can be driven faster than its input by energy delivered to the output from a spring. To control the energy delivered to the system from rotate spring 56 during a return shift operation, I employ an unloading spring 120 that acts in opposition to the rotate spring 56. When the shift arm 61 is in its home position as shown in full lines, it is urged by unloading spring 120 clockwise against a displaceable stop ledge 121 of spring biased frame mounted pivoted stop lever 122. Stop lever 122 is moved clockwise to an ineffective position by forward movement of the rod 93 acting on nose 123. When the shift arm 61 is in its broken line position as shown in FIG. 3, end 124 of unloading spring 20 engages a frame mounted disabling member 125. It will thus be seen that the force of spring 120 will be active on moving parts only during actual displacement of the shift arm 61 between its active positions.

Having thus described my method and preferred illustrative apparatus for performing my method, 1 define the subject matter patented by the following claims.

lclaim:

l. The method from performing case shift operation in a typewriter including a type element having first and second pluralities of characters carried thereby, a case shift member having two operative positions corresponding respectively to said first and second pluralities of characters, a character selecting member having a home position and movable to a displaced position corresponding to an individual character within either of said pluralities of characters, a motion transmission connecting said type element with said case shift member and with said character selection member for positioning said type element in response to the algebraically combined positions of said members, means defining a cycle of operation of said typewriter during which said character selecting member is selectively displaced from its home position to said displaced position and returned to its home position, wherein the improvement comprises the steps of:

during one part of a cycle of operation moving said case shift member from one of its operative positions to the other and moving said character selecting member in a sense that is subtractive of the motion of said case shift member, and during a different part of the same cycle, moving said character selecting member in a sense opposite to the first said motion thereof while retaining said case shift member in one of its operative positions. 2. A typewriter including a type element having first and second pluralities of characters carried thereby, a case shift member having two operative positions corresponding respectively to said first and second pluralities of characters, a character selecting member having a home position and movable to a displaced position corresponding to an individual character within either of said pluralities of characters, a motion transmission connecting said type element with said case shift member and with said character selection member for positioning said type element in response to the algebraically combined positions of said members, a selectively activatable source of cyclical motion, a multidisplacement character selection motion converter operatively connected between said cyclical motion source and said character selection member for moving said character selection member from its home position to said displaced position during a portion of said cyclical motion, and for moving said character selection member from its displaced position to its home position during a different portion of said cyclical motion, wherein the improvement comprises:

means impositively urging said case shift member toward a first one of its operative positions,

means for retaining said case shift member in a second one of its operative positions when said case shift member is moved thereto,

a selectively activatable case shift motion converter operatively connected between said cyclical motion source and said case shift member for positively driving said case shift member from said first operative position thereof to said second operative position thereof during a first one of said cycle portions, and

selectively operable shift control means for contemporaneously activating said cyclical motion source, activating said case shift motion converter, and controlling said character selection motion converter to move said character selection member during said one of said cycle portions in a sense that is subtractive of motion of said case shift member.

3. A typewriter is defined in claim 2 wherein said motion transmission comprises:

a flexible strand operatively connecting said type element with said character selection member and said case shift member.

4. A typewriter as defined in claim 2 further having print impact means and letter feed means operatively connnected to said source of cyclical motion for normal operation thereby and wherein the improvement further comprises:

means operated by said shift control means for rendering said print impact means and said letter feed means ineffective during operation of said shift control means.

5. A typewriter as defined in claim 2 further having a manually operable keyboard including a plurality of character selection keys, means connecting said character selection keys with said motion source and said character selection motion converter and wherein said selectively operable shift control means comprises:

a manually operable two position shift key for controlling selection of operation thereof.

6. A type writer as defined in claim further having print impact means and letter feed means operatively connected to said source of cyclical motion for normal operation thereby and wherein the improvement further comprises:

means operated by said shift control means for rendering said print impact means and said letter feed means ineffective during operation of said shift control means.

7. A typewriter as defined in claim 5 wherein said retaining means COmpl'lSCSZ a latch for engaging said case shift member,

means normally resiliently biasing said latch to a nonretaining condition, and

means responsive to the position of said shift key for resiliently biasing said latch toward a retaining condition when said shift key is one of its two positions.

8. A typewriter including a type element having first and second pluralities of characters carried thereby, a case shift member having two operative positions corresponding respectively to said first and second pluralities of characters, a character selection member having a home position and movable to a displaced position corresponding to an individual character within either of said pluralities of characters, a motion transmission connecting said type element with said case shift member and with said character selection member for positioning said type element in response to the algebraically combined positions of said members, a selectively activatable source of cyclical motion, a multidisplacement character selection motion converter operatively connected between said cyclical motion source and said character selection member for moving said character selection member from its home position to said displaced position during a portion of said cyclical motion, and for moving said character selection member from said displaced position to its home position during a different portion of said cyclical motion, wherein the improvement comprises:

means impositively urging said case shift member toward a first one of its operative positions,

releaseable retaining means for securing said case shift member in a second one of its operative positions,

a selectively activatable case shift motion converter operatively connected between said cyclical motion source and said case shift member for limiting the displacement of said case shift member by said impositively urging means during movement of said case shift member from said second operative position to said first operative position during one of said cycle portions, and

selectively operable shift control means for contemporaneously activating said motion source, activating said case shift motion converter, controlling said character selection motion converter to move said character selection member during said one cycle portions in a sense that is subtractive of motion of said case shift member, and controlling said retaining means to release said case shift member therefrom.

9. A typewriter as defined in claim 8 wherein the improvement further comprises:

means conditioned by said shift means and responsive to said cyclical motion for effecting said release of said retaining means.

10. A typewriter as defined in claim 8 wherein said cyclical motion source comprises an overrunnable clutch and wherein the further improvement comprises:

spring means operatively connected to said case shift member for opposing the action of said resilient urging means, and

means operative when said case shift member is in its second operative position for rendering said spring means ineffective. 11. A typewriter as defined in claim 8 wherein said motion transmission comprises:

a flexible strand operatively connecting said type element with said character selection member and said case shift member.

12. A typewriter as defined in claim 8 further having print impact means and letter feed means operatively connected to said source of cyclical motion for normal operation thereby and wherein the improvement further comprises:

means operated by said shift control means for rendering said print impact means and said letter feed means ineffective during operation of said shift control means.

13. A typewriter as defined in claim 8 further having a manually operable keyboard including a plurality of character selection keys, means connecting said character selection keys with said motion source and said character selection motion converter and wherein said selectively operable shift control means comprises:

a manually operable two position shift key for controlling selection of operation thereof.

14. A typewriter as defined in claim 13 further having print impact means and letter feed means operatively connected to said source of cyclical motion for normal operation thereby and wherein the improvement further comprises:

means operated by said shift control means for rendering said print impact means and said letter feed means ineffective during operation of said shift control means.

15. A typewriter as defined in claim 13 wherein said retaining means comprises a latch for engaging said case shift member, and further comprising:

means normally biasing said latch to a nonretaining condition,

means responsive to the position of said shift key for resiliently biasing said latch to a retaining condition when said shift key is in one of its two operative positions, and

said case shift motion converter being responsive to said cyclical motion for effecting said release of said retaining means at a predetermined cyclic time whenever said latch is biased to its nonretaining condition.

16. A shift key mechanism comprising a depressable two position keylever, an interposer supported operatively adjacent said keylever and being engageable with a power means to be displaced thereby, a case shift mechanism operable in response to displacement of said interposer by said power means, wherein the improvement comprises:

a bellcrank having a generally horizontal arm and a generally vertical arm pivotally mounted at a point intermediate said arms on said keylever,

a spring connected to said bellcrank for urging said bellcrank toward a normal position relative to said keylever,

a projection carried by said horizontal arm for engaging said interposer in force transfer relationship for moving said interposer to a position for cooperatively engaging said power means,

means providing a drive connection between said interposer and said bellcrank for pivoting said bellcrank from its normal position relative to said shift keylever upon displacement of said interposer by said power means following depression of said shift keylever, and

a latch operable upon pivoting of said bellcrank to retain said bellcrank in its pivoted position relative to said keylever so long as said keylever remains depressed,

whereby said projection is moved to displace said interposer by either displacement of said pivot upon depression of said keylever or by pivoting of said bellcrank by said spring upon upward movement of said keylever. 

1. The method from performing case shift operation in a typewriter including a type element having first and second pluralities of characters carried thereby, a case shift member having two operative positions corresponding respectively to said first and second pluralities of characters, a character selecting member having a home position and movable to a displaced position corresponding to an individual character within either of said pluralities of characters, a motion transmission connecting said type element with said case shift member and with said character selection member for positioning said type element in response to the algebraically combined positions of said members, means defining a cycle of operation of said typewriter during which said character selecting member is selectively displaced from its home position to said displaced position and returned to its home position, wherein the improvement comprises the steps of: during one part of a cycle of operation moving said case shift member from one of its operative positions to the other and moving said character selecting member in a sense that is subtractive of the motion of said case shift member, and during a different part of the same cycle, moving said character selecting member in a sense opposite to the first said motion thereof while retaining said case shift member in one of its operative positions.
 2. A typewriter including a type element having first and second pluralities of characters carried thereby, a case shift member having two operative positions corresponding respectively to said first and second pluralities of characters, a character selecting member having a home position and movable to a displaced position corresponding to an individual character within either of said pluralities of characters, a motion transmission connecting said type element with said case shift member and with said character selection member for positioning said type element in response to the algebraically combined positions of said members, a selectively activatable source of cyclical motion, a multidisplacement chaRacter selection motion converter operatively connected between said cyclical motion source and said character selection member for moving said character selection member from its home position to said displaced position during a portion of said cyclical motion, and for moving said character selection member from its displaced position to its home position during a different portion of said cyclical motion, wherein the improvement comprises: means impositively urging said case shift member toward a first one of its operative positions, means for retaining said case shift member in a second one of its operative positions when said case shift member is moved thereto, a selectively activatable case shift motion converter operatively connected between said cyclical motion source and said case shift member for positively driving said case shift member from said first operative position thereof to said second operative position thereof during a first one of said cycle portions, and selectively operable shift control means for contemporaneously activating said cyclical motion source, activating said case shift motion converter, and controlling said character selection motion converter to move said character selection member during said one of said cycle portions in a sense that is subtractive of motion of said case shift member.
 3. A typewriter is defined in claim 2 wherein said motion transmission comprises: a flexible strand operatively connecting said type element with said character selection member and said case shift member.
 4. A typewriter as defined in claim 2 further having print impact means and letter feed means operatively connnected to said source of cyclical motion for normal operation thereby and wherein the improvement further comprises: means operated by said shift control means for rendering said print impact means and said letter feed means ineffective during operation of said shift control means.
 5. A typewriter as defined in claim 2 further having a manually operable keyboard including a plurality of character selection keys, means connecting said character selection keys with said motion source and said character selection motion converter and wherein said selectively operable shift control means comprises: a manually operable two position shift key for controlling selection of operation thereof.
 6. A type writer as defined in claim 5 further having print impact means and letter feed means operatively connected to said source of cyclical motion for normal operation thereby and wherein the improvement further comprises: means operated by said shift control means for rendering said print impact means and said letter feed means ineffective during operation of said shift control means.
 7. A typewriter as defined in claim 5 wherein said retaining means comprises: a latch for engaging said case shift member, means normally resiliently biasing said latch to a nonretaining condition, and means responsive to the position of said shift key for resiliently biasing said latch toward a retaining condition when said shift key is one of its two positions.
 8. A typewriter including a type element having first and second pluralities of characters carried thereby, a case shift member having two operative positions corresponding respectively to said first and second pluralities of characters, a character selection member having a home position and movable to a displaced position corresponding to an individual character within either of said pluralities of characters, a motion transmission connecting said type element with said case shift member and with said character selection member for positioning said type element in response to the algebraically combined positions of said members, a selectively activatable source of cyclical motion, a multidisplacement character selection motion converter operatively connected between said cyclical motion source and said character selection member for movIng said character selection member from its home position to said displaced position during a portion of said cyclical motion, and for moving said character selection member from said displaced position to its home position during a different portion of said cyclical motion, wherein the improvement comprises: means impositively urging said case shift member toward a first one of its operative positions, releaseable retaining means for securing said case shift member in a second one of its operative positions, a selectively activatable case shift motion converter operatively connected between said cyclical motion source and said case shift member for limiting the displacement of said case shift member by said impositively urging means during movement of said case shift member from said second operative position to said first operative position during one of said cycle portions, and selectively operable shift control means for contemporaneously activating said motion source, activating said case shift motion converter, controlling said character selection motion converter to move said character selection member during said one cycle portions in a sense that is subtractive of motion of said case shift member, and controlling said retaining means to release said case shift member therefrom.
 9. A typewriter as defined in claim 8 wherein the improvement further comprises: means conditioned by said shift means and responsive to said cyclical motion for effecting said release of said retaining means.
 10. A typewriter as defined in claim 8 wherein said cyclical motion source comprises an overrunnable clutch and wherein the further improvement comprises: spring means operatively connected to said case shift member for opposing the action of said resilient urging means, and means operative when said case shift member is in its second operative position for rendering said spring means ineffective.
 11. A typewriter as defined in claim 8 wherein said motion transmission comprises: a flexible strand operatively connecting said type element with said character selection member and said case shift member.
 12. A typewriter as defined in claim 8 further having print impact means and letter feed means operatively connected to said source of cyclical motion for normal operation thereby and wherein the improvement further comprises: means operated by said shift control means for rendering said print impact means and said letter feed means ineffective during operation of said shift control means.
 13. A typewriter as defined in claim 8 further having a manually operable keyboard including a plurality of character selection keys, means connecting said character selection keys with said motion source and said character selection motion converter and wherein said selectively operable shift control means comprises: a manually operable two position shift key for controlling selection of operation thereof.
 14. A typewriter as defined in claim 13 further having print impact means and letter feed means operatively connected to said source of cyclical motion for normal operation thereby and wherein the improvement further comprises: means operated by said shift control means for rendering said print impact means and said letter feed means ineffective during operation of said shift control means.
 15. A typewriter as defined in claim 13 wherein said retaining means comprises a latch for engaging said case shift member, and further comprising: means normally biasing said latch to a nonretaining condition, means responsive to the position of said shift key for resiliently biasing said latch to a retaining condition when said shift key is in one of its two operative positions, and said case shift motion converter being responsive to said cyclical motion for effecting said release of said retaining means at a predetermined cyclic time whenever said latch is biased to its nonretaining condition.
 16. A shift key meChanism comprising a depressable two position keylever, an interposer supported operatively adjacent said keylever and being engageable with a power means to be displaced thereby, a case shift mechanism operable in response to displacement of said interposer by said power means, wherein the improvement comprises: a bellcrank having a generally horizontal arm and a generally vertical arm pivotally mounted at a point intermediate said arms on said keylever, a spring connected to said bellcrank for urging said bellcrank toward a normal position relative to said keylever, a projection carried by said horizontal arm for engaging said interposer in force transfer relationship for moving said interposer to a position for cooperatively engaging said power means, means providing a drive connection between said interposer and said bellcrank for pivoting said bellcrank from its normal position relative to said shift keylever upon displacement of said interposer by said power means following depression of said shift keylever, and a latch operable upon pivoting of said bellcrank to retain said bellcrank in its pivoted position relative to said keylever so long as said keylever remains depressed, whereby said projection is moved to displace said interposer by either displacement of said pivot upon depression of said keylever or by pivoting of said bellcrank by said spring upon upward movement of said keylever. 